The present invention relates generally to washers and more particularly to a washer that uses a single, fixed fluid level to wash small, medium, and large clothes load sizes.
A washer typically is a home appliance for washing clothes and other loads automatically. A conventional washer (sometimes referred to as a washing machine) includes system controls and a waterproof wash tub having a sump area that acts as a reservoir for fluid. Within the wash tub may be located a perforated wash basket. The wash basket holds a clothes load while the perforations permit fluid to flow into and out of the wash basket. Inside the wash basket may be an impeller to aid in moving the clothes load through the fluid. Consumers typically use various compositions of fluids and solutions inside the washer, with water solutions being most commonly seen in practice.
The use of a washer is relatively straightforward. After a consumer fills the wash basket with clothes, the consumer typically makes a few decisions before starting the load. For example, the consumer may decide how big the load is (small, medium, large, extra large), what temperature the water will be for the wash and rinse cycles (cold/cold, warm/cold, warm/warm, hot/cold), and the type of clothes load (delicate, knit, permanent press, heavy). The consumer also may decide how long the wash and rinse cycles should last (number of minutes, usually based on how soiled the clothes are) and how much detergent to add.
After setting the washer controls, adding detergent, and pressing a start button, the machine fills the tub with a volume of fresh water according to the selected load size, among other factors. The fresh water mixes with the detergent to create a bath of wash liquid. The impeller moves and flexes the clothes in the wash liquid to remove soil from the clothes. After some time passes, the washer drains the wash liquid and soil. A motor spins the perforated wash basket to remove most of the remaining wash liquid from the clothes. Then, the system may refill with fresh water one or more times and move the clothes more to rinse the clothes clean. The machine then drains the rinse liquid and spins the perforated wash basket again to produce clean clothes. At any time during this washing or rinsing process, a recirculation pump may spray wash liquid over the clothes for better cleaning action.
From an energy standpoint, a washer cleans clothes through chemical, mechanical, and thermal energy. Detergent in water solution provides the chemical energy that acts to remove and suspend soils. The impeller movements (and sometimes a recirculation pump) provide mechanical energy into the clothes and water. The water transmits impeller mechanical energy to the clothes. Heated water provides thermal energy that may act directly on the soil. An increase in the level of any of these three forms of energy will generally improve the cleaning capability of the washer up to some level. For example, an increase in the amount of detergent (an increase in the chemical energy) would improve the cleaning capability of the washer.
Increasing the chemical, mechanical, or thermal energy level of a washer may require that the level of one of the remaining two forms of energies be altered. Conventionally, altering the level of one of the remaining two forms of energies means moving it away from its preferred level to a less than desirable level. In particular, problems arise when this trade-off in applied energy involves the chemical and mechanical forms of energy.
For the wash liquid, there conventionally are two approaches to improving chemical energy. Both approaches involve increasing detergent concentration; that is detergent-to-water ratio. One way is to add more detergent to a given volume of fresh water. However, this is undesirable since it increases consumer detergent costs. A second way is to decrease the volume of fresh water used for the same detergent amount that consumers are accustomed to using. Consumers prefer this low water bath method since it saves water resources and does not require them to alter their detergent habits. However, two problems result when increasing detergent concentration by lowering the volume of fresh water used: over-suds and over-torque.
Over-suds is an excess build-up of soapsuds. One cause is the use of too much mechanical energy from the impeller or from a recirculating pump. Over-sudsing may reduce the overall cleaning performance since the detergent used to create the excessive soapsuds is not available for removing soil from the clothes. Over-sudsing may also cause ‘suds lock.’ Suds lock is a buildup of sudsy fluid in the wash tub and sump. As the sudsy fluid fills the area between the sides of the wash basket and the wash tub, these suds cause a significant drag force on the spinning wash basket. With suds lock, the drag forces may be greater than the forces that the motor may provide. This may stop the wash process prematurely.
Over-torque refers to an excess amount of torque force needed by the impeller to move the water and clothes. In a deep fill washer system, a large amount of water causes the clothes to become buoyant and float up and away from the impeller, thereby minimizing the impeller's direct influence on the clothes movement. In a low fill washer system, there is a loss of buoyancy lift, which puts more clothes in contact with the impeller, thereby increasing the impeller's direct influence on the clothes movement. This may result in a higher torque required to move the impeller. When over-torque conditions exist, the motor may not be able to provide the required torque forces, and the wash process may be prematurely stopped.
A low fill washer system typically is preferred because it conserves water resources. The over-suds and over-torque problems for a low fill washer system have been addressed in the industry by a trade-off between chemical and mechanical energy forms. In other words, where a washer manufacturer increases the detergent concentration by using a low water bath, a decrease in the overall mechanical energy conventionally meets this increase in chemical energy.
One way to reduce the overall mechanical energy imparted into the wash liquid bath is to pulse the energy applied to the recirculation pump during recirculation. This causes less agitation of the wash liquid and, in turn, less suds. However, this results in an uneven saturation of the clothes load. Alternatively, the drive system of the impeller may be powered for a shorter on-time or supplied with power for fewer times during a wash or rinse cycle. However, a change in the time that power is supplied to the impeller relative to the total wash time alters the ‘duty cycle’ of the washer system. Decreasing the duty cycle of the system reduces the average torque imparted by the impeller into the wash liquid. Although this reduces the tendency to over-suds, the reduction in mechanical energy results in a reduced clothes motion. In turn, the reduction in the motion of the clothes may degrade the cleaning performance on certain soils, especially with larger loads. Accordingly, conventional decrease in the overall mechanical energy to address the over-suds and over-torque problems in low fill washer systems has resulted in its own set of problems that still need to be resolved.